The present invention relates generally to pressurized fluid systems and more particularly; but not by way of limitation, to an apparatus which operates to establish a secondary path for a pressurized fluid when a pressure of the fluid falls above or below a selected operating pressure range.
Pressurized fluid systems are typically provided with pressure control and relief capabilities to prevent the possibility of injury to humans and damage to equipment in the event of an overpressure situation. Such pressure control systems often use a pressure responsive member such as a buckling pin that mechanically fails when subjected to a large increase in fluid pressure. Failure of the pressure responsive member allows a valve assembly to operate to establish an appropriate overpressure path for the fluid (such as by establishing a bypass path for the fluid or by shutting down a flow of the fluid).
While such systems typically operate to provide protection from overpressure conditions, there are also applications where it is desirable to detect and abate underpressure conditions as well. For example, a rupture in a pressurized pipeline or similar network can result in a sudden drop in system pressure as the fluid escapes to the external environment. In such a case it is desirable to activate a valve assembly to establish a secondary path for the fluid (such as an upstream shutoff valve which halts further flow of the fluid) until the rupture condition can be remediated.
There is therefore a continued need for improvements in the art to provide a pressure control system that operates when a pressure of a pressurized fluid falls outside a selected operating range, both above the range in an overpressure context as well as below the range in an underpressure context. It is to such improvements that the present invention is directed.
The present invention is generally directed to detecting and abating an underpressure condition and an overpressure condition in a pressurized fluid.
In accordance with preferred embodiments, a pressure control system includes a collapsible buckling pin having an intermediate portion and opposing first and second ends. A valve assembly is coupled to the first end of the buckling pin and applies a compressive force to the buckling pin in relation to a pressure of the fluid.
The valve assembly respectively establishes a secondary path for the fluid when the pressure of the fluid exceeds an upper operational limit and when the pressure of the fluid falls below a lower operational limit. The secondary path is preferably a shut off path, but a bypass path can also be used as desired.
A control assembly is coupled to the second end of the buckling pin. The control assembly comprises a retractable support member moveable between an extended position and a retracted position. A biasing member applies a retraction force to the support member to urge the support member to the retracted position.
The compressive force applied to the buckling force generates a retention force between the second end of the pin and the support member to retain the support member in the extended position. The buckling pin thus remains supported between the valve assembly and the control assembly as long as the pressure is above the lower operational limit.
In the event of an overpressure condition in which the pressure of the fluid exceeds the upper operational limit, the intermediate portion of the buckling pin is mechanically deformed between the valve assembly and the support member. Conversely, in the event of an underpressure condition in which the pressure of the fluid falls below the lower operational limit, the retention force provided by the compression of the buckling pin is insufficient to overcome the retraction force of the biasing member.
The support member thus retracts to the retracted position and the second end of the buckling pin advances past the support member. In this way, the control assembly acts as a xe2x80x9ctrap doorxe2x80x9d to allow the buckling pin to be mechanically displaced without being mechanically deformed. In both cases (overpressure condition and underpressure condition), the mechanical displacement of the buckling pin allows the valve assembly to establish the shut off path.
These and various other features and advantages which characterize the claimed invention will become apparent upon reading the following detailed description and upon reviewing the associated drawings.